dontdump(5)							File Formats Manual						       dontdump(5)

NAME

       dontdump - defines which classes of kernel memory pages are not dumped when a kernel panic occurs

VALUES

   Failsafe
   Default
       (Allow the kernel to choose which classes to dump.)

   Allowed values
       Integer values from to

       The integer value should be the sum of the integer values for the excluded classes as follows:

	      2 : Unused pages
	      4 : User pages
	      8 : Buffer cache
	      16 : Kernel text pages
	      32 : Process stack
	      64 : File-system Metadata
	      128 : Kernel dynamic data
	      256 : Kernel static data
	      512 : Unused superpage pool

   Recommended values
       (Allow the kernel to choose which classes to dump.)

       The  value  the	kernel usually chooses is = The kernel chooses these classes because they are not usually useful in debugging kernel prob-
       lems.

DESCRIPTION

       On large systems, the time required to dump system memory when a kernel panic occurs can be excessive or even prohibitive, depending on how
       much  physical  memory is installed in the system.  Fast-dump capabilities controlled by the and parameters provide a means for restricting
       kernel dumps to specific types of information:

	       . Unused Physical Memory
	       . User Process
	       . Buffer Cache
	       . Kernel Code
	       . Process Stack
	       . File-System Metadata
	       . Kernel Dynamic Data
	       . Kernel Static Data
	       . Unused Superpage Pool

       The command, and its associated configuration file control which of these memory classes are to be included in the memory dumps	associated
       with a kernel panic.  On rare occasions, the system may panic before crashconf(1M) is run during the boot process.  On those occasions, the
       configuration can be set using the and tunables.

       The bit-map value stored in specifies which of these memory classes are not to be included in the memory dumps  associated  with  a  kernel
       panic.

       The  default  value  for  this  parameter is The system determines whether or not to dump classes of memory based on the type of crash that
       occurs, in this case.

       Note that certain types of system crash, require a full crash dump.  Also, the system operator may request a full crash dump  at  the  time
       the dump is taken.  In either of these cases, a full dump will be performed regardless of the classes selected using

   Who Is Expected to Change This Tunable?
       Only HP Field engineers should change the value of this tunable.

   Restrictions on Changing
       Changes to this tunable take effect at next reboot. Use to change the selection of pages to take effect immediately.

   When Should the Tunable Be Turned On?
       This  tunable  should be turned on to exclude certain classes of pages from being dumped when there is a system crash.  This can be done to
       speedup the dump.

   What Are the Side Effects of Turning the Tunable On?
       If pages necessary for analyzing the dump are excluded, then the dump may not be useful for identifying the cause of the system crash.

   When Should the Tunable Be Turned Off?
       The tunable is turned off by default.

   What Are the Side Effects of Turning the Tunable Off?
       The system decides the page classes that must not be dumped based on the type of crash.	The dump may take longer.

   What Other Tunables Should Be Changed at the Same Time?
       The tunable should not contain the same page classes as

WARNINGS

       All HP-UX kernel tunable parameters are release specific.  This parameter may be removed or have its meaning changed in future releases	of
       HP-UX.

       Installation  of  optional  kernel  software, from HP or other vendors, may cause changes to tunable parameter values.  After installation,
       some tunable parameters may no longer be at the default or recommended values.  For information about the effects of installation  on  tun-
       able  values,  consult  the documentation for the kernel software being installed.  For information about optional kernel software that was
       factory installed on your system, see at

AUTHOR

       was developed by HP.

SEE ALSO

       crashconf(1M), alwaysdump(5).

							     Tunable Kernel Parameters						       dontdump(5)